Motorists won’t mess with you. Pedestrians won’t step in front of you. It looks like the chainsaw on this Russian rig spins the front wheel so you won’t even have to do much pedaling. I suppose the designer could have taken the chain off the chainsaw and still used the engine, but that would have taken a lot of the danger/fun out of it.

I tried to use a chainsaw engine before and they have no torque unless they are really reving. I have trouble believing it will move a 150 lb person from a start so the rear wheel drive is very necessary and cannot be disabled. It is likely a bump start to get the engine running but I don’t see a clutch if the rider wants to disengage. Finally, take a close look at the front forks. It looks like the holes drilled into them for the motor mounting hardware caused them to buckle.